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Advanced Mendelian Genetics

Advanced Mendelian Genetics. EQ: Do Mendel’s principals of genetics apply to all organisms or just to pea plants?. Independent Assortment. To determine if the segregation of one pair of alleles affects the segregation of another pair of alleles, Mendel performed a two-factor cross.

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Advanced Mendelian Genetics

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  1. Advanced Mendelian Genetics EQ: Do Mendel’s principals of genetics apply to all organisms or just to pea plants?

  2. Independent Assortment • To determine if the segregation of one pair of alleles affects the segregation of another pair of alleles, Mendel performed a two-factor cross.

  3. The Two-Factor Cross:F1 • Mendel crossed purebred plants that produced round yellow peas (genotype RRYY) with purebred plants that produced wrinkled green peas (genotype rryy) • All of the offspring produced round green peas (RrYy) RRYY x rryy

  4. (Do not copy) • The alleles for round (R) and yellow (Y) are dominant over the alleles for wrinkled (r) and green (y)

  5. The Two-Factor Cross: F2 • Mendel crossed the heterzygous F1 plants (RrYy) with each other to determine if the alleles would segregate from each other in the F2 generation RrYy x RrYy

  6. The Two Factor Cross: F2 • The Punnett square predicts a 9:3:3:1 ratio in the F2 generation

  7. Independent Assortment • The alleles for seed shape segregated independently of those for seed color. This principle is known as independent assortment. • Genes that segregate independently do not influence each other’s inheritance.

  8. Independent assortment • This principle of independent assortment states that genes for different traits can segregate independently during the formation of gametes. • Independent assortment helps account for many genetic variations observed in living things.

  9. Incomplete Dominance • When one allele is not completely dominant over another it is called incomplete dominance. • In incomplete dominance, the heterozygous phenotype is between the two homozygous phenotypes

  10. Incomplete Dominance • A cross between red (RR) and white (WW) four o’clock flowers produced pink-colored flowers (RW)

  11. Codominance • In codominance, both alleles contribute to the phenotype • In certain varieties of cows, the allele for white hair is codominant with the allele for brown hair

  12. Multiple Alleles • Genes that are controlled by more than two alleles are said to have multiple alleles. • A rabbit’s coat color is determined by a single gene that has at least four different alleles. • Human eye color works in this way.

  13. X-Linked Traits • Some traits are only found on the X chromosome which determine gender. • Because males have only 1 X chromosome (Xy) they are more predisposed to genetic disorders than are females (XX) because males only have one copy of the gene while females have two. • Example of a sex-linked trait is colored blindness.

  14. Question 1 • Traits controlled by two or more genes are called • Multiple-allele traits • Polygenic traits • Codominant traits • Hybrid traits

  15. Question 2 • In four o’clock flowers, the allele for red flowers and white flowers show incomplete dominance. Heterozygous four o’clock plants have • Pink flowers • White flowers • Half white flowers and half red flowers. • Red flowers

  16. Question 3 • Mendel’s principals apply to • Pea plants only • Fruit flies only • All organisms • Only plants and animals

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